And the extraterrestrial ocean is currently being fed more than a hundred times more oxygen than previous models had suggested, according to provocative new research.

That amount of oxygen would be enough to support more than just microscopic life-forms: At least three million tons of fishlike creatures could theoretically live and breathe on Europa, said study author Richard Greenberg of the University of Arizona in Tucson.

"There's nothing saying there is life there now," said Greenberg, who presented his work last month at a meeting of the American Astronomical Society's Division for Planetary Sciences. "But we do know there are the physical conditions to support it."

In fact, based on what we know about the Jovian moon, parts of Europa's seafloor should greatly resemble the environments around Earth's deep-ocean hydrothermal vents, said deep-sea molecular ecologist Timothy Shank.

"I'd be shocked if no life existed on Europa," said Shank, of the Woods Hole Oceanographic Institution, who was not involved in the new study.

Video: Hydrothermal Vents on Earth

Despite the promising new estimates, it's too early to do more than speculate about how Europan life might have evolved. A closer look—perhaps by a NASA orbiter now in development—will be needed to tell exactly how chemicals are distributed on Europa and how the moon's geologic history might have contributed to life's chances.

Europa's Shiny New Coat

Italian astronomer Galileo Galilei discovered Europa in 1610. But it wasn't until Galileo, the NASA spacecraft, reached the Jupiter system in 1995 that scientists were able to study the moon in detail.